Fuel injection pumps

ABSTRACT

A fuel injection pump includes a pump barrel in which is reciprocably mounted a plunger which has a helical or like groove communicating with a pumping chamber defined at the end of the plunger, there being provided in the pump barrel a spill port through which fuel can escape from the pumping chamber when the port is exposed by the groove, the spill port being formed in such a manner as to define a wall which is presented to the flow of fuel through the spill port whereby the velocity of such flow is minimized.

United States Patent Inventor Stanley Robert Bagshaw Hemel Hempstead, England Appl. No. 856,369 Filed Sept. 9, 1969 Patented Sept. 28, 1971 Assignee C.A.V. Llmlted Warple Way, Acton, London, England Priority Sept. 24, 1968 Great Britain 45242/68 FUEL INJECTION PUMPS 1 Claim, 2 Drawing Figs.

us. Cl 417/494, 417/498 Int. Cl F04b 7/04, F04b 39/10 Field of Search 103/2.l,

References Clted UNITED STATES PATENTS 2,044,814 6/1936 Rothrock 103/154 X 2,325,524 7/1943 Links 103/154 X 2,713,310 7/1955 Muraszew 103/154 X FOREIGN PATENTS 1,033,798 6/1966 Great Britain 103/21 1,238,121 6/1960 France l03/2.1

Primary Examiner-Carlton R. Croyle Assistant Examiner-R. E. Gluck Attorney-Holman & Stern ABSTRACT: A fuel injection pump includes a pump barrel in which is reciprocably mounted a plunger which has a helical or like groove communicating with a pumping chamber defined at the end of the plunger, there being provided in the pump barrel a spill port through which fuel can escape from the pumping chamber when the port is exposed by the groove, the spill port being fonned in such a manner as to define a wall which is presented to the flow of fuel through the spill port whereby the velocity of such flow is minimized.

Q S l2 IAa I Q44 8 7 I |6 9 29 S 1/ I 'g, x 17 FUEL INJECTION PUMPS This invention relates to fuel injection pumps of the kind comprising a pump body, a pump barrel mounted within the pump body, a reciprocable plunger slidable within the barrel, a spill groove formed on the plunger, and a spill port formed in the barrel, the spill port opening into a gallery in the pump body and serving when placed in communication with the groove to allow surplus fuel to escape from the pumping chamber of the injection pump.

The object of the invention is to provide such a pump in a simple and convenient form.

According to the invention in a pump of the kind specified the spill port is staggered in the form thereby defining a wall presented towards the inner ends of the port, the action of the staggered port being to reduce the velocity at which fuel escapes through the spill port into the gallery.

In the accompanying drawings:

FIG. 1 is a sectional side elevation of one example of a fuel injection pump in accordance with the invention, and

FIG. 2 is a view showing a modified part of the pump of FIG. 1.

With reference to FIG. 1 there is provided a pump body 9 in which is mounted a pump barrel 8. The pump body defines a gallery extending around the barrel 8 and the gallery is in communication with a fuel inlet (not shown) formed in the pump body. In the barrel is formed an axial bore which accommodates a reciprocable pumping plunger 10 and in use, the plunger is arranged to be moved inwardly by the action of a rotary cam 7 in timed relationship with an associated engine and to be moved outwardly by the action of a coiled compression spring 17.

During inward movement of the plunger fuel is displaced from the pumping chamber defined by the bore and the end of the plunger 10 past a nonretum valve 12 to an outlet 11 and to an associated injection nozzle 13. During outward movement of the plunger fuel is admitted to the pumping chamber through a pair of diametrical ports 14, 14a formed in the barrel 8 and communicating with the aforesaid gallery. The fuel flows into the pumping chamber when the ports 14, 140 are uncovered during the outward movement of the plunger.

In known manner the plunger 10 is provided with a helical or like groove 16 which communicates with the pumping chamber and which at some point during the inward movement of the plunger communicates with the port 14 (hereinafter called the spill port) to allow fuel to escape from the pumping chamber into the gallery 15. The relative angular setting of the plunger 10 and pump barrel 8 can be adjusted so that the quantity of fuel delivered at each inward stroke of the plunger can be varied. This may be achieved by adjustment of either the plunger or the pump barrel but as shown, the plunger is movable angularly by means of a rack bar 29.

It is well known that the velocity at which the fuel travels through the spill port 14 is very high and erosion of the wall of the gallery can be caused. In order to reduce the velocity the spill port 14 is formed in staggered fashion so that the flow of fuel is turbulent. The turbulent flow causes restriction to the flow of fuel thereby minimizing the erosion of the wall of the gallery. In one example the spill port is defined by inner and outer blind bores the axes of which are offset. The inner blind bore is aligned with the spill port 14a and the blind bores communicate with each other to enable fuel flow to occur through the port. By the provision of the staggered bores a wall is provided which faces the inner end of the spill port, the wall acting to promote the turbulent flow of fuel. FIGS. 1 and 2 show alternative ways of positioning the outer blind bore relative to the inner bore.

I claim:

1. A fuel injection pump of the kind comprising a pump body, a pump barrel mounted within the pump body, a reciprocable plunger slidable within the barrel and defining a pumping chamber, a spill groove formed on the plunger, a spill port formed in the barrel, a gallery surrounding the pump barrel and into which the spill port opens, said gallery having a wall defined by the body part said spill port serving when placed in communication with the groove to allow surp us fuel to escape from the pumping chamber, said spill port being formed by inner and outer blind bores the axes of which are offset, the blind bores communicating with each other to define a flow-restricting wall presented towards the inner end of the spill port, the action of the wall being to restrict the rate and reduce the velocity at which fuel escaping through the spill port impinges on the wall of the gallery. 

1. A fuel injection pump of the kind comprising a pump body, a pump barrel mounted within the pump body, a reciprocable plunger slidable within the barrel and defining a pumping chamber, a spill groove formed on the plunger, a spill port formed in the barrel, a gallery surrounding the pump barrel and into which the spill port opens, said gallery having a wall defined by the body part, said spill port serving when placed in communication with the groove to allow surplus fuel to escape from the pumping chamber, said spill port being formed by inner and outer blind bores the axes of which are offset, the blind bores communicating with each other to define a flow-restricting wall presented towards the inner end of the spill port, the action of the wall being to restrict the rate and reduce the velocity at which fuel escaping through the spill port impinges on the wall of the gallery. 